The present invention relates to a solid-state laser, and more particularly to a Yb-doped crystal for a solid-state laser and a method of preparing the same.
The solid-state laser doped with a Yb activation element had been studied from a long time ago. After a diode excitation had been succeeded, the Yb-doped solid-state laser has become useful. The first observation of laser action was obtained by pumping Yb-doped yttrium aluminum garnet (Yb: YAG) with standard Si-doped GaAs light emission diodes. This is disclosed in the J. Appl. Phys. Lett. 19(1) pp. 11-13, 1971. As a result of recent development of the semiconductor laser diodes, absorption and emission by laser diode excitation have been observed at room temperature. This is disclosed in Optical Letters, 15(16) pp. 1089-1091. Yttrium aluminum garnet YAG (Y3A15012) is available as a host material to be doped with Yb, which is disclosed in Tech. Digest. ASSL, pp. 230-232, 1995. Garnet system crystals such as glass and LuAg(Lu3A15O12) are available as a host material to be doped with Yb, which is disclosed in Tech. Digest. ASSL, pp. 224-226, 1995. Apatite system fluoride crystals such as FAP(Ca5(PO4)3F) are available as a host material to be doped with Yb, which is disclosed in Tech. Digest. ASSL, pp. 188-191, 1993. The above crystals may be grown by Czochralski method disclosed in Tech. Digest. ASSL, pp. 230-232, 1995.
In the Japanese laid-open patent publications Nos. 5-27980 and 6-107430, it is disclosed to add Yb as a sensitizer into solid state laser crystals.
In the prior art, however, certain techniques for growth of a crystal for a solid state laser with a high emission efficiency had not been established because it had not been found what factor actually provide a great deal of influence to emission efficiency and fluorescence lifetime of the Yb-laser. Even if the desired result could unexpectedly be obtained by accidental combinations of various conditions, such uncertain technique could not be industrially applicable and could not progress the crystal growth technique.
In the above circumstances, it had been establish a certain method of growth of or treatment to a crystal for the Yb-doped solid state laser by explication of any physical factors which provide maximum contribution to improve the emission efficiency of the Yb-doped solid state laser.